This page helps: http://hoxtonowl.com/forums/topic/audiounits-compilation-tips/
download the sample from http://developer.apple.com/library/ios/#samplecode/CoreAudioUtilityClasses/
Move the CoreAudio folder to: /Library/Developer/CoreAudio
create a symb. link from /Applications/Xcode.app/Contents/Developer/Extras/
In my case Extras did not exist so
sudo mkdir Extras
sudo ln -s /Library/Developer/CoreAudio CoreAudio
check in XCode that "Juce Library Code"->"Juce AU Wrapper" files are found and not red
now it's possible to compile the AU
for vst3 vst:
Go to Steinberg.net register as developer and download the vst3 SDK
copy the "VST3 SDK" Folder to /User/<your username>/SDKs/ (create folder SDKs...)
next you need the vstsdk2.4 which isn't available on steinbergs site
I found it here -> https://github.com/aardvarkk/soundfind
download it and copy the vstsdk2.4 folder to /User/<your username>/SDKs/
now XCode throws a couple of errors in the audioeffect.cpp and other files just accept the compiler casts.
my last error was that there was no VST3 Dir at /User/<your username>/Library/Audio/Plug-Ins/
create the dir and tata! it works
testet in Ableton Live....
hope this helps...
would be nice if someone adds this to the "How to use this Framework.txt" in the audio plugin demo project ;-)